Method and system for managing data transmission from a plurality of sensor devices included in a tyre

ABSTRACT

Wireless transmission from sensor devices included in tires is coordinated by a receiving unit associated with the tire, or transmission coordinator. In more detail, every sensor device is made aware of an overall time window available for transmission, and based on at least this information, it calculates a dedicated timeslot for the transmission of its data within such time window. This coordinated transmission makes possible a strong reduction of the probability of collisions and transmission errors, and reduces the number of transmissions, so as to comply with the limited power resources available at each sensor device.

CROSS REFERENCE TO RELATED APPLICATION

This application is a national phase application based onPCT/IT2007/000901, filed Dec. 20, 2007.

FIELD OF THE INVENTION

The present invention relates to a method and a system for managingtransmission of data measured by a plurality of sensors included in atyre fitted on a vehicle. Said sensors could comprise for exampleaccelerometers, and/or strain gauges, and/or pressure sensors, and/ortemperature sensors.

BACKGROUND OF THE INVENTION

The incorporation of electronic devices within pneumatic tyres is takinga greater importance in order to increase safety of vehicles. Tyreelectronics may include sensors and other components suitable forobtaining information regarding the behavior of a tyre, as well asvarious physical parameters thereof, such as for example temperature,pressure, number of tyre revolutions, vehicle speed, etc. Suchinformation may become useful in tyre monitoring and/or alarm systems.Furthermore, active control systems of the vehicle may be based oninformation sent from sensor devices included within the tyres.

Integrated tyre electronics systems have conventionally been powered bya variety of techniques and different power generation systems.

A typical solution for powering tyre electronics systems is the use of anon-rechargeable battery, which may cause inconveniences to a tyre usersince proper electronics system operation is dependent on periodicbattery replacement. As a matter of fact, batteries tend to depletetheir energy storage quite rapidly when powering electronic applicationscharacterized by complex levels of functionality. Furthermore,conventional batteries typically contain heavy metals that are notenvironmentally friendly and which present disposal concerns. Moreover,performances of conventional batteries are often influenced bytemperature: in particular, the functioning of such batteries is notreliable at low temperatures.

Another known method for powering tyre monitoring systems is a couplingof radio-frequency (RF) power between an antenna disposed on the vehiclein close proximity with another antenna included within the electronicdevice disposed in the tyre. This typically requires antennas disposedin vehicle portions frequently exposed to damage from road hazards, andthus may lead to many drawbacks.

The use of energy scavenging or harvesting elements, e.g. based onpiezoelectricity, has also been proposed for powering tyre monitoringsystems. Piezoelectricity is a property of certain materials, such asquartz, Rochelle salt, and certain solid-solution ceramic materials suchas lead-zirconate-titanate (PZT), of generating electrical charge whenmechanically stressed.

For example, WO 2005/067073 discloses a tyre comprising a piezoelectricflexing element associated with an energy storage device (e.g. acapacitor). The piezoelectric flexing element is mounted in cantileverfashion in a housing so as to be positioned substantially along a planeorthogonal to a radial direction of said tyre and, so that a first endof the piezoelectric element is restrained to the housing. A loadingmass is coupled to the second end of the piezoelectric flexing element.A small gap is formed between the inner walls of the housing and theouter surface of the loading mass, in order to allow limited flexure ofthe piezoelectric element. The housing including the piezoelectricelement is mounted in a tyre portion in correspondence of a tread areaof the tyre, preferably on the inner surface of the tyre. Thepiezoelectric element flexes under the action of the radial accelerationwhen the tyre rotates. The loading mass and the gap are chosen toobtain: a) small entity oscillations of the flexure elementsubstantially during a complete revolution of the tyre, when the tyrerotates at low speed; b) large entity oscillations of the flexureelement substantially only during the passage of the tyre portionincluding the piezoelectric element in the contact patch.

Typically, wireless transmission is employed in order to send tyreperformance information outside the tyre, to a receiver disposed on thevehicle body, so that electronic devices disposed within a wheeltypically include a transmitter associated to an antenna.

EP 1484200 relates to a communication system for communicating between atire/wheel assembly and a vehicle body, which is provided with awheel-side communication device mounted to the wheel and which rotatestogether with the wheel, and a body-side communication device mounted ina fixed position to the vehicle body. Communication takes place betweenthe wheel-side communication device and the body-side communicationdevice according to the rotational position of the wheel. According toEP 1484200, when one of the wheel-side communication device and thebody-side communication device receives a signal from the other, thereception changes cyclically as the wheel rotates. There is a patternbetween the change in that reception and the change in the rotationalposition of the wheel, in which the reception improves when the actualrotational position of the wheel matches a specific rotational position.The system disclosed in EP 1484200 selectively performs communicationbetween the wheel-side communication device and the body-sidecommunication device at a rotational position of a wheel, from among aplurality of rotational positions of the wheel, with the exception of arotational position where the communication state between thecommunication devices may be poor. Moreover, the communication system ofEP 1484200 may also be provided with: i) a rotational position detectingdevice that detects a rotational position of the tire/wheel assembly;and ii) a transmission timing determining device that determines acommunication timing based on the relationship between the rotationalposition of the wheel detected by the rotational position detectingdevice and a received signal level, which is the level of a signalreceived from one of the body-side communication device and thewheel-side communication device by the other.

In another document, namely EP 1536392, the object of performing astable function of the system and of increasing the probability of thetransmission and reception even in the presence of a dead point, i.e. apoint at which the receive intensity does not reach the receive limit,is said to be achieved by a wheel condition monitoring system having atransmitter which is installed on an individual rotatable wheel totransmit a condition of the wheel and a receiver which is installed onthe vehicle body side to receive the condition of the wheel sent fromthe transmitter, wherein the rotation speed of the wheel is detected(e.g. with an accelerometer), and data indicating the condition of thewheel are sent from the transmitter to the receiver at intervals inaccordance with the detected rotation speed of wheel. In particular, thesystem is configured so that transmission is achieved at intervalscorresponding to the rotation speed of wheel. Therefore, even if a deadpoint at which transmission and reception are impossible is present, theprobability that transmission and reception can be accomplished byseveral times of transmission can be increased, and the system canperform its functions stably. More in detail, when the receiver receivesa plurality of pieces of data sent from the transmitter installed oneach of a plurality of wheels, first data transmission from thetransmitter is performed after each waiting time set for eachtransmitter has elapsed, so that a problem of transmission overlaps withthe transmission of electric waves from another wheel in terms of time,can be overcome.

EP1826029 discloses a system in which acquired wheel information, suchas temperature data and inflation pressure data, is surely transmittedfrom a transmitter in a status where the transmitter is not located in adead space, by controlling timing wherein the transmitter acquires thewheel information, a transmission time width and transmitting timing ofthe data to be transmitted from the transmitter by radio. In particular,the wheel information acquiring system disclosed in EP 1826029 acquireswheel information of the wheel during rotation, and comprises:

-   -   a first communication device that is attached to the wheel and        detects wheel information associated with the wheel during        rotation, and wirelessly transmits the detected wheel        information from a wheel side; and    -   a second communication device that is provided apart from the        wheel and that receives and acquires the wheel information        transmitted by the first communication device,        wherein the first communication device has a maximum value of        rotation speed specified for the wheel during rotation to which        the first communication device is attached (e.g. comprised in a        range between 90 km/h and 300 km/h); and wherein when a        transmission time width of one packet of the wheel information        transmitted by the first communication device is represented by        T₁, and an expected minimum rotation period-which is determined        according to the maximum value of the rotation speed        prespecified in the first communication device is represented by        R₁, T₁ is set so as to satisfy T₁≦R₁·½, preferably T₁≦R₁· 1/12.

WO2004/030950 discloses a telemetry unit provided for mounting inside apneumatic tyre, which includes a piezoelectric element supported in ahousing, with an actuator arranged for contact with the element, todeflect the element in response to external forces acting on theactuator during rotation of the tyre. For every rotation of the tyre,cyclic pulses of electrical charge are generated by the deflection ofthe element. The charge is stored and utilized under a power consumptionprotocol including the steps of: initiating power to a data measurementcircuit for measuring data from the environment local to the unit;disabling power to the data measurement circuit; initiating power to adata transmission circuit; transmitting data from the measurementcircuit; and disabling power to the transmission circuit. The powerconsumption protocol therefore minimizes consumption of the generatedpower, during measurement and transmission of data by the unit.

EP 1487682 discloses a method for monitoring the behavior of a tyreduring running, the method comprising the steps of: acquiring andstoring, at least temporarily, a first curve representing theacceleration profile of a first point of the tread area of said tyre,located on a meridian plane of said tyre; acquiring and storing, atleast temporarily, at least a second curve representing the accelerationprofile of a second point of the tread area of said tyre, locatedsubstantially on said meridian plane; comparing said first and secondcurves, or parameters derived thereof; determining the behavior of saidtyre from said comparison.

EP 1676112 discloses a method and a system for determining a corneringangle of a tyre fitted on a vehicle during a running of said vehicle ona rolling surface. The method comprises the steps of: estimating alength of a contact region between said tyre and said rolling surface,said length being measured at a distance from the equatorial plane ofthe tyre; estimating a load exerted on said tyre; estimating a camberangle to which said tyre is subjected; and deriving such cornering anglefrom said camber angle, tyre load and contact region length.

EP 1794007 discloses a method and a system for determining a corneringangle of a tyre fitted on a vehicle during a running of said vehicle ona rolling surface. The method comprises the steps of: determining thelateral acceleration of a portion of the tyre tread spaced apart fromthe equatorial plane of said tyre; determining a rotation speed of saidtyre; and determining said cornering angle from said lateralacceleration and said rotation speed, by using characteristic curves oflateral acceleration amplitude versus predetermined values of corneringangle for at least one rotation speed.

SUMMARY OF THE INVENTION

According to the Applicant, a complete tyre sensor system should includea plurality of sensor devices located at predefined positions within atyre, for the purpose of obtaining a more detailed description of theinteraction between the tyre and the ground, which appears to benecessary for implementing reliable vehicle control systems based oninformation derived from the tyres.

For example, a plurality of accelerometers could be fixed to the innersurface of the tyre and disposed on the same meridian plane of the tyre,in order to derive information related to the length of the contactregion between the tyre and the ground in different points of thecontact region itself, and/or in order to derive various otherparameters, such as the tyre load, the cornering and/or the camber angleto which the tyre is being subjected, the current and the potentialfriction between the tyre tread surface and the ground, etc.

A reliable collection of data from a plurality of sensor devicesincluded within a tyre should as much as possible avoid collisionsbetween information (typically sent in form of data packets) sent fromdifferent sensor devices at the same time. In fact, collisions betweenpackets sent from different sensor devices requires multipleretransmission of the missed packets, and/or multiple transmissions ofall the packets from the sensor devices, which appears to bedisadvantageous for devices which have a very limited available power.This latter issue becomes even more critical in case of use of energyscavenging components for the powering of the sensor devices, as it maybe the case of a tyre integrated sensor system in which use ofnon-rechargeable and disposal-problematic batteries is refrained.

The Applicant has thus faced the problem of providing a reliable and lowpower consuming transmission from a plurality of sensor devices includedwithin a tyre.

The Applicant has found that this problem can be solved by coordinatingthe transmission of the various sensor devices. In more detail, everysensor device is made aware of an overall time window available fortransmission, and based on at least this information it calculates adedicated timeslot for the transmission of its data within such timewindow. This coordinated transmission makes possible a strong reductionof the probability of transmission errors, and reduces the number oftransmissions, so as to comply with the limited power resourcesavailable at each sensor device.

In a first aspect, the invention relates to a method for managingtransmission of data from a plurality of sensor devices included in atyre fitted on a vehicle, the method comprising:

-   -   providing said plurality of sensor devices at predefined        respective positions in said tyre;    -   providing a transmission coordinator on said vehicle, outside of        said tyre;    -   rotating said tyre and having said plurality of sensor devices        obtaining data related to a condition of said tyre during        rotation thereof;    -   causing said plurality of sensor devices to wirelessly transmit        the obtained data;        wherein said causing said plurality of sensor devices to        wirelessly transmit said obtained data comprises:    -   sending timing information from said transmission coordinator,        said timing information being at least related to a maximum        allowed time interval for the transmission of the obtained data        from said plurality of sensor devices;    -   at each sensor device of said plurality of sensor devices,        receiving said timing information and calculating at least one        respective transmission timeslot for the transmission of the        obtained data within said maximum allowed time interval, so as        to obtain a respective plurality of non-overlapping transmission        timeslots;    -   at each sensor device of the plurality of sensor devices,        waiting for the respective calculated at least one transmission        timeslot and wirelessly transmitting the obtained data within        the respective calculated at least one transmission timeslot.

In a second aspect, the invention relates to a system for monitoring atyre fitted on a vehicle comprising:

-   -   a plurality of sensor devices being adapted to obtain data        related to a condition of said tyre during rotation thereof and        to wirelessly transmit the obtained data outside of said tyre;    -   a transmission coordinator being adapted to receive said        obtained data transmitted by said plurality of sensor devices;        wherein    -   said transmission coordinator is further adapted to send timing        information to said plurality of sensor devices, said timing        information being at least related to a maximum allowed time        interval for the transmission of the obtained data from said        plurality of sensor devices;    -   each sensor device of said plurality of sensor devices is        further adapted to receive said timing information and calculate        at least one respective transmission timeslot for the        transmission of the obtained data within said maximum allowed        time interval, so as to obtain a respective plurality of        non-overlapping transmission timeslots; and    -   each sensor device of the plurality of sensor devices is further        adapted to wait for the respective calculated at least one        transmission timeslot and to wirelessly transmit the obtained        data within the respective calculated at least one transmission        timeslot.

The present invention, in at least one of the abovementioned aspects,may comprise one or more of the preferred features hereinafterdescribed.

The maximum allowed time interval is preferably at most equal to a timeinterval required for one complete revolution of said tyre, morepreferably at most equal to a half of said time interval required forone complete revolution of said tyre. This is advantageous forimplementing a very precise vehicle control system, which needsinformation related to the interaction between the tyre and the groundat every tyre revolution.

In preferred embodiments, at least one sensor device is “designated” asmaster sensor device. The master sensor device is adapted to send idleinformation being related to a readiness of said plurality of sensordevices to receive said timing information. Moreover, the transmissioncoordinator is adapted to send said timing information consequently of areception of said idle information.

Advantageously, each sensor device of said plurality of sensor devicescomprises an electrical circuit being adapted to store electrical energygenerated in consequence of the rotation of the tyre. The scavenging ofenergy from the rotation of the tyre allows disposal problems related tothe use of batteries in the sensor devices to be avoided.

The master sensor device can be adapted to send said idle informationwhen a voltage across its respective electrical circuit is higher than apredetermined threshold. This allows beginning the coordination of thetransmissions from the different sensor devices when the latter ones areready to operate.

The timing information sent by the transmission coordinator may be alsorelated to a maximum allowed acquisition time interval for theacquisition of data related to a condition of said tyre by the pluralityof sensor devices. In such case, each sensor device may organize itsacquisition and transmission activities in a very simple and lowpower-consuming way.

It may be convenient to provide that said maximum allowed acquisitiontime interval and said plurality of non-overlapping calculatedtransmission timeslots do not overlap with each other. In such case, nopeaks of power are needed, with a possible better overall powermanagement in each sensor device.

The transmission coordinator may be further adapted to process the datareceived by the sensor devices, so as to derive a condition of saidtyre. Suitable processing algorithms could be implemented at thetransmission coordinator for deriving various parameters characterizingthe behavior of the tyre during rolling.

While the method and the system of the invention try to avoid, as muchas possible, the retransmissions from the sensor devices, in exceptionalcases the transmission coordinator may be further adapted to address aretransmission request of at least one data portion to at least onesensor device, particularly in case of missed reception of said at leastone data portion transmitted from at least one sensor device.

The at least one sensor device may thus further be adapted to retransmitsaid at least one data portion in consequence of a reception of saidretransmission request. The retransmission is performed within themaximum allowed time interval.

The at least one sensor device may be also adapted to calculate arespective retransmission timeslot based on the timing informationpreviously received by the transmission coordinator, and to retransmitsaid at least one data portion within said respective calculatedretransmission timeslot. Preferably, said calculated respectiveretransmission timeslot and the plurality of non-overlappingtransmission timeslots do not overlap with each other, so as to avoidcollisions between transmitted packets and retransmitted packets.

In preferred embodiments, the plurality of sensor devices comprises atleast two sensor devices disposed substantially at the same meridianplane of the tyre (e.g. the sensor devices may be disposed within acircumferential angle of at most 5°). This allows a very precisemonitoring of the contact region between the tyre and the ground.

In more preferred embodiments, each sensor device of said plurality ofsensor devices comprises an accelerometer. Said accelerometer mayadvantageously be adapted to measure acceleration in at least twodirections, preferably three directions.

Conveniently, each sensor device of said plurality of sensor devices isfixed to an inner surface of the tyre, which could be simplyaccomplished, e.g., by using a suitable adhesive.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features and advantages of the present invention will be madeapparent by the following detailed description of some exemplaryembodiments thereof, provided merely by way of non-limiting examples.The description will make reference to the attached drawings, wherein:

FIG. 1 schematically shows a transverse section of a tyre having threesensor devices disposed on the inner surface of a tyre, usable in apreferred embodiment of the present invention;

FIG. 2 schematically shows an equatorial section of a tyre having threegroups of sensor devices disposed on the liner internal surface, usablein a further preferred embodiment of the present invention;

FIG. 3 shows a first exemplary sequence of time frames for thecoordinated data transmission of three nodes/sensor devices located onthe same meridian plane of a tyre;

FIG. 4 shows a second exemplary sequence of time frames for thecoordinated data transmission of three nodes/sensor devices located onthe same meridian plane of a tyre;

FIG. 5 shows a third exemplary sequence of time frames for theretransmission of lost data packets transmitted by three nodes/sensordevices located on the same meridian plane of the tyre.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS OF THE INVENTION

FIG. 1 shows an exemplary tyre 1 comprising an internally hollowtoroidal structure formed by a plurality of components, primarily by acarcass, terminating in two beads, each formed along an innercircumferential edge of the carcass, for securing the tyre to acorresponding supporting rim (not shown in FIG. 1). The tyre 1 typicallycomprises at least one pair of annular reinforcing cores, called beadcores, which are inserted in the said beads. The carcass is a supportingstructure formed by at least one reinforcing ply which includes textileor metallic cords, axially extending from one bead to the otheraccording to a toroidal profile, the ends of which are associated with acorresponding bead core. In radial tyres, the aforesaid cords lieessentially in planes containing the axis of rotation of the tyre.

In a radially external position to the carcass, an annular structure isplaced, known as belt structure, typically comprising one or more stripsof rubberized fabric, wound on top of each other. A tread made fromelastomeric material, wound around the belt structure, and usuallymolded with a relief pattern for the rolling contact of the tyre withthe road is also added. Two sidewalls, made from elastomeric material,each extending outwards in radial direction from the outer edge of thecorresponding bead, are also placed on the carcass, in axially opposedpositions.

In tubeless tyres the inner surface of the carcass is normally coveredwith at least one liner layer, i.e. with one or more layers of airtightelastomeric material. The tyre 1 may further comprise other knownelements, such as edges, strips and fillers, according to the specificdesign of the tyre.

At least two sensor devices comprising sensor components adapted tomeasure a quantity related to the interaction between the tyre and theground are disposed substantially along the same meridian plane withinthe tyre 1. For the purposes of the present invention, by “meridianplane” of a tyre it has to be intended any plane comprising the rotationaxis of the tyre. In preferred embodiments, the sensor components couldbe accelerometers. Strain gauges could also be used in alternative to orin combination with accelerometers. For the purposes of the presentinvention, the expression “substantially along the same meridian plane”contemplates a certain amount of misalignment of the sensor devices withrespect to said meridian plane, that can be expressed in terms of theangle comprised between the meridian planes defined by the sensor devicepositions. Preferably, the tolerated misalignment may correspond to anangle not greater than 5°, more preferably not greater than 3°, evenmore preferably not greater than 1°. More particularly, the sensordevices are disposed in correspondence of the crown portion T of thetyre 1, i.e., the portion of the tyre 1 axially extended between thesidewalls of the tyre 1. Preferably, as shown in the embodiment of FIG.1, at least three sensor devices could be disposed along substantiallythe same meridian plane of the tyre 1.

In the embodiment shown in FIG. 1, three sensor devices 11, 12, and 13are disposed on the internal surface of the tyre 1, on the inner linersurface. A first sensor device ills disposed substantially at theequatorial plane of the tyre 1. Two other sensor devices 12, 13 aredisposed substantially on the same meridian plane of the tyre 1 inshoulder regions of the crown portion T of the tyre 1. Such sensordevice disposition allows a monitoring the general behavior of the fullinteraction area between the tyre and the ground; for instance when thetyre is cornering the signals derived from the two shoulder sensordevices 12 and 13 change relative to each other: this change could betracked in order to gain information related to a cornering angle of thetyre 1, or for identifying a given maneuver of the vehicle on which thetyre 1 is fitted. Methods disclosed in some of the documents cited inthe background of the invention could be exploited in order to deriveinformation related to the behavior of the tyre and/or to theinteraction of the tyre with the ground during running of a vehicle.

In order to ensure a good monitoring of the whole interaction areabetween the tyre and the ground, the sensor devices should be separatedfrom each other of a certain distance. However, with regards to thesensor devices disposed in the shoulder regions, they should be disposedsufficiently far away from the sidewalls, so that they can providesignals in almost every condition of travel. In this respect, it has tobe noticed that vehicle regulations, such as for example the camber, incombination with particular maneuvers of the vehicle (e.g. sharp bends)may cause transient partial loss of interaction between shoulderportions of the tread near the sidewall and the ground. Preferably, ashoulder sensor device could be disposed at a distance from theequatorial plane of the tyre comprised between 15% and 30% of the treadwidth, more preferably between 18% and 28% of the tread width, even morepreferably between 20% and 25% of the tread width. For example, in atyre having a tread width of 195 mm, two shoulder sensor devices may bedisposed on opposite sides with respect to the equatorial plane, each ata distance of 45 mm thereof.

Preferably, at least one sensor device is adapted to measure theacceleration of the respective monitored point of the tyre 1 in at leasttwo directions orthogonal to each other. More preferably, all the sensordevices are adapted to measure the acceleration with respect to at leasttwo directions orthogonal to each other. For example, in FIG. 1 the X, Yand Z local axes represent three directions that for the purposes of thepresent description are named respectively:

-   -   centripetal direction Z, which is a radial direction of said        tyre,    -   tangential direction Y, which is a direction tangential to the        circumference of said tyre,    -   lateral direction X, which is a direction orthogonal to both        said centripetal and tangential directions.        Preferred directions for the measurements are the centripetal        and the tangential direction.

In FIG. 2 a further embodiment of a tyre usable in the present inventionis shown, in which several groups of sensor devices 21, 22, and 23 areassociated to a tyre 1. Each group of sensor devices 21, 22, and 23comprises sensor devices disposed substantially along the same meridianplane of the tyre 1, as disclosed above with reference to FIG. 1.Preferably, the groups of sensor devices are located in acircumferential position spaced one from each other of substantially thesame angle. For example, in FIG. 2 three groups of sensor devices areshown, spaced from each other of an angle of substantially 120°. As faras the disposition of the sensor device within each group 21, 22 or 23in the embodiment of FIG. 2, reference is made to what disclosed abovewith reference to FIG. 1.

The use of a plurality of groups of sensor devices as shown in FIG. 2allows the achievement of more accuracy and reliability of themeasurements performed by the sensor devices, as well as a bettermonitoring of the entire wheel turn.

The sensor devices 11, 12, 13 and/or 21, 22, 23, may typically comprise(further to the sensor component) a power supply, preferably aself-generating power device (e.g., a piezoelectric device) generatingelectrical energy thanks to the deformations subjected by the tyreduring rotation and storing the same in an electrical circuit, aprocessing unit, a transmitter and an antenna connected to thetransmitter. A receiver (which is also connected to the antenna),preferably a low-rate, low-power, consuming wake-up radio receiver, isalso included in each of the sensor devices.

The sensor devices 11, 12, 13 and/or 21, 22, 23 are in wirelesscommunication with a receiving device, typically including an antenna, areceiver connected to the antenna and a processing unit. The receivingdevice also comprises a transmitter (which is also connected to theantenna). Such receiving device may be preferably disposed on thevehicle. In preferred embodiments, a respective receiving device isassociated to each tyre fitted on a vehicle, for receiving data from andfor controlling the transmission of the plurality of sensor devicesincluded therein. Thus, for example, a car could be equipped with fourreceiving devices, each being in bidirectional communication with thesensor devices included in the associated tyre.

In operation, during running of the tyres the sensor components of thesensor devices perform a measurement, so that an electrical signal isgenerated and acquired carrying information related to, e.g., theacceleration of the respective points of the tyre to which they areassociated. The acquired signals are then wirelessly transmitted by thesensor devices to the associated receiving device, typically by means ofradio frequencies. The transmitted signals are typically in form of datapackets. In preferred embodiments the acquisition and the transmissionoperations are performed in different, non-overlapping time intervals,so as to reduce the probability of peak power consumption. Typically, incase of use of a self-powering device for the powering of the sensordevices, the operations of the sensor devices are started when thevoltage generated by the self-powering device is above a predefinedthreshold. As it will be explained in more detail below, the timing ofthe transmission of the different sensors included in a tyre iscontrolled by the associated receiving device, which thus acts as atransmission coordinator for the sensor devices included in theassociated tyre. In order to set the timing for data transmission,timing information sent from the transmission coordinator is receivedand processed by the sensor devices.

Each receiving device, or transmission coordinator, receives the signals(or data packets) sent by the sensor devices included in the respectiveassociated tyre. The processing unit included in each transmissioncoordinator can thus perform the processing needed in order to derive acondition of the associated tyre, e.g. its behavior and/or parameterscharacterizing the operation of the tyre (load, cornering angle, camberangle, etc.). As stated above and described in detail below, eachtransmission coordinator also transmits timing information to the sensordevices for controlling the timing of the data transmission from eachsensor device included in the respective associated tyre.

By collecting the information from all the tyres, a maneuver (e.g.braking, acceleration, cornering, etc.) being performed by the tyres orby the vehicle can thus be identified. Moreover, a critical conditionbeing reached by the tyres or by the vehicle during such maneuver (forexample due to aquaplaning) could also be identified. In such case, analarm signal could be generated, to cause a counter-action to controlthe vehicle, e.g. by the driver or by auto-control systems of thevehicle. These “high-level” operations could be performed by a centralreceiving device or system control host (e.g. implemented in or incommunication with the on-board vehicle computer) being in communicationwith all the transmission coordinators.

As already introduced above, the timing of the transmission of theplurality of sensor devices included in a tyre is controlled by theassociated receiving device, which thus acts as a transmissioncoordinator for the sensor devices included in the associated tyre. Moreparticularly, in order to set the transmission schedule of the pluralityof sensor devices, an implicit method is used, in which each sensordevice determines its own allocated timeslot for transmission of theacquired data based on timing information sent by the transmissioncoordinator. Timing information can be sent by the transmissioncoordinator via a so called “beacon packet”, including few data allowingeach sensor device to suitably schedule its own operations, particularlythe respective transmission timeslot. The suitable operation schedulecould be performed by each sensor device based on the received timinginformation and, possibly, on information stored at each sensor deviceitself. The implicit method of generating the transmission scheduleenables a simplification of the architecture of the sensor devices,since a low-rate wake-up receiver could be used in the sensor devices.Moreover, a remarkable reduction in the power consuming needed for thereception of the timing information can be reached, since long scheduleinstruction packets are not needed, which is advantageous especially incase of use of self-powering (or energy scavenging) devices for poweringthe sensor device. In order to gain information useful for vehiclecontrolling, synchronization with the rotation of the tyre isadvantageously implemented, so that the timing information is sent bythe transmission coordinator at each rotation of the tyre, and the datapackets are also sent by the sensor devices to the transmissioncoordinator at each rotation of the tyre.

In practice, the sub-system formed by the sensor devices included in atyre and the associated transmission coordinator is configured as apico-network, having a coordinator (the transmission coordinator) andmultiple nodes (the plurality of sensor devices). In the pico-network,the multiple nodes are independent and do not interact with each other.Moreover, the transmission order of the nodes is known to thecoordinator and to the nodes. The ordering can be predetermined andstored both at the coordinator and the nodes. Furthermore, all nodes areallocated the same amount of transmission time. It is also assumed thatthe differences in time of arrival at plurality of nodes of the beaconpacket including timing information sent by the coordinator arenegligible as compared with the transmission timeslots.

The following parameters could be exemplarily defined for describing thetiming information sent by the transmission coordinator and/orderived/calculated from the sensor devices/nodes of the network:

T_(slot): is the allotted timeslot for one node or sensor device totransmit to the transmission coordinator;

T_(frame): is the time it takes for n nodes to transmit data, i.e. thetotal time interval formed by the plurality of non-overlapping timeslotsof duration T_(slot);

n: is the total number of network nodes, i.e. the total number of sensordevices in one tyre;

T_(tx0): is the total transmission time allocated by the transmissioncoordinator (including possible retransmissions) for the network in agiven transmission cycle;

T_(tx): is the remaining time in a given transmission cycle;

The communication protocol between the nodes or sensor devices includedin the tyre and the associated transmission coordinator may comprise aninitialization phase in which one of the sensor devices, beingdesignated as “master” node, sends one or more beacon-request packet(s)to the transmission coordinator. This beacon request may correspond to areadiness condition reached by the sensor devices for the transmissionof data. For example, this readiness condition could correspond to thefact that a sufficient level of power is stored in an electrical circuitassociated with an energy scavenging component included in the sensordevices, which typically occurs after a certain number of tyrerotations. The beacon-request packet(s) advantageously comprise(s)information related to the current rotation speed of the tyre (and,possibly, the rotation angle at which the sensor device is located),acquired by a sensor component included in the master sensor device. Forexample, such information could be an acceleration curve sensed andacquired by the sensor device, from which the rotation speed (and,possibly, the rotation angle at which the sensor device is located)could be derived.

In the initialization phase, the transmission coordinator receives thebeacon-request packet(s) and derives the current rotation speed of thetyre (and, possibly, the rotation angle at which the master sensordevice is located). Based on the derived information, the transmissioncoordinator can calculate how much time to allocate for the transmissionof all the sensor devices/nodes of the network. The maximum time allowedfor the transmission of data by all the sensor devices may preferably beset as being lower than the time required for an entire tyre rotation,more preferably lower than a half of the time required for an entiretyre rotation. This allows maintaining synchronization of the datatransmission with the rotation of the tyre, which is advantageous formonitoring in a very precise and substantially continuous way theinteraction between the tyre and the ground during rotation.

The transmission coordinator then generates a beacon packet carryingtiming information needed for the calculation, at the sensor devices, ofthe respective transmission timeslots. For example, the followinginformation could be included in the beacon packet:

-   -   Total network data transmission time (T_(tx0));    -   Time left for transmission (T_(tx));    -   Number of nodes/sensor devices currently present in the network        (n).

The number of nodes/sensor devices could also be permanently stored ateach node/sensor device, so that the transmission coordinator could beprogrammed for sending only timing information. In a preferredembodiment, additional information related to a time interval to bereserved within T_(tx0) for lost packet retransmissions could beprovided in the beacon packet. For example, data related to a certainpercentage of T_(tx0) (e.g. 10%) could be included in the beacon packetsent by the transmission coordinator. However, it has to be understoodthat also this data could be permanently stored at each node/sensordevice.

The beacon packet comprising timing information could be retransmittedperiodically (e.g. at the start of each frame) until the transmissioncoordinator has received valid data packets from all the nodes/sensordevices included within the associated tyre. These valid data packetscould be acknowledgement beacons sent by the nodes/sensor devices, or,preferably, the actual data acquired by the nodes/sensor devices duringrotation of the tyre and transmitted to the transmission coordinator. Ateach retransmission of the beacon carrying timing information performedby the transmission coordinator, the time left for transmission T_(tx)is updated.

In preferred embodiments, the beacon packet(s) comprising timinginformation is (are) sent by the transmission coordinator at every turnof the tyre. The timing for a subsequent beacon transmission could bederived by the transmission coordinator based on the data acquired andtransmitted by the sensor devices, from which the transmissioncoordinator could derive the rotation speed of the tyre.

The communication protocol between the nodes or sensor devices includedin the tyre and the associated transmission coordinator then comprisesthe transmission phase, in which the nodes/sensor devices perform allthe operations needed for setting up the scheduling of the datatransmission based on the timing information received from thetransmission coordinator.

In particular, upon receiving the beacon packet comprising timinginformation sent by the transmission coordinator, each node preferablyturns off the respective receiver, so as to save power. In addition, itestimates when to turn on the receiver again to listen to the beacon ofthe next transmission cycle. For example, the receiver of eachnode/sensor device could be turned on after the respective datatransmission, or at the end of the total network data transmission timeT_(tx0), or, in case of activation of a retransmission mechanism forlost data packets, at the estimated time for the beginning of theretransmission time interval.

Moreover, each node/sensor device uses the parameters T_(tx), T_(tx0), nreceived via the beacon packet sent by the transmission coordinatorand/or stored in a memory of the node/sensor device itself, toimplicitly generate a TDMA (Time Division Multiple Access) schedulingfor data transmission, formed by a plurality of non-overlappingtransmission timeslots. More particularly, considering threenodes/sensor devices included in a tyre and located on the same meridianplane as in the exemplary tyre embodiment of FIG. 1, each node/sensordevice could be associated with an order number a₁=1, a₂=2, a₃=3. Basedon the order number and the timing information from the beacon packet,each node/sensor device is able to calculate its assigned transmissiontimeslot.

For example, each node/sensor device can be adapted to determine theduration T_(slot) of the time interval for transmission by using theparameter T_(tx), i.e. the time left for transmission, as being equal tothe useful frame for transmission (see parameter T_(frame) above), andsimply dividing T_(tx), for the number n of nodes/sensor devices. Inother cases, the duration T_(frame) useful for data transmission (and tobe divided by the number n of nodes/sensor devices in order to determineT_(slot)) could be derived by subtracting to T_(tx) time intervalsrequired by the communication protocol, such as for example timeintervals for retransmissions, and/or time intervals for dataacquisition. In still other examples, the communication protocol may seta plurality of frames for each data transmission, so that eachnode/sensor device is assigned a corresponding plurality of transmissiontimeslots. In any case, once the parameter T_(slot) is determined, atime parameter T_(wait) _(—) _(initial) could be derived by each of thenodes/sensor devices using the above mentioned order numbers and thesimple formula (T_(wait) _(—) _(initial))_(i)=(a_(i)−1)*T_(slot). Foreach node/sensor device i, the calculated parameter (T_(wait) _(—)_(initial))_(i); corresponds to the time that the node/sensor deviceshould wait before data transmission to the transmission coordinator,corresponding to the TDMA scheduling. Data transmission is thenperformed by each node/sensor device in the respective assignedtransmission timeslot (or timeslots, if a plurality of transmissionframes is set). The transmitted data packets are labeled with anidentifier associated with each node/sensor device. After completion ofdata transmission, each node/sensor device comes back in an operativemode in which it could acquire/process the next data to be transmitted,and/or activate its receiver for listening beacons from the transmissioncoordinator for the next transmission cycle, to be preferably performedat the successive tyre turn.

This implicit scheduling mechanism has the advantage of avoidingreceiving complex scheduling instructions from the transmissioncoordinator at each node/sensor device, thus saving listening power.Moreover, the TDMA scheduling has the additional advantage of stronglyreducing (or even nullifying) the probability of collisions between datapackets sent by different nodes/sensor devices, so as to reduce or evenavoid the need of retransmissions. This further reduces the powerconsumption needed at each node/sensor device for enabling correct datareception at the transmission coordinator.

Example 1

FIG. 3 shows a first exemplary sequence of time frames for thecoordinated data transmission of three nodes/sensor devices located onthe same meridian plane of a tyre. It is assumed that a beacon(represented by “B” in FIG. 3) including timing information is sent by atransmission coordinator associated to the three nodes/sensor devices atthe beginning of a time window provided for data transmission. It isalso assumed that data acquisition is performed in a different timewindow.

As shown by FIG. 3, the transmission coordinator sends a first beaconwith timing information. The first beacon is correctly received by Node2, but not received by Node 1 (designated as Master Node) and by Node 3(as represented by the two “X”s in the first frame of FIG. 3). Thus, thetransmission coordinator, the Node 1 and the Node 3 remain in await/listen mode for all the first frame, while the Node 2 calculatesand waits for its assigned timeslot in the first frame, in which ittransmits a first data packet. After transmission of the first datapacket, the Node 2 enters in a process/wait status, in which itprocesses the next data packet to be transmitted in the next assignedtimeslot. In this operative mode, the receiver of Node 2 is switchedoff.

At the beginning of the second frame, another beacon is sent by thetransmission coordinator (with updated timing parameters), since thelatter did not receive data from all the nodes/sensor devices. Thissecond beacon is lost by Node 2, which has its receiver switched off:however, Node 2 already possesses all the information needed for its owntransmission scheduling, since it received the first beacon with thetiming information. On the other hand, Master Node 1 and Node 3 havetheir receiver switched on, and correctly receive the beacon with timinginformation. Based on the received timing information, both Master Node1 and Node 3 calculate their assigned transmission timeslots. Inparticular, Master Node 1 immediately transmits a first data packet,whereas Node 3 waits for its assigned timeslot and then transmits itsfirst data packet. Both Master Node 1 and Node 3 then enter in aprocess/wait status, in which they keep their receiver switched off.Between the transmissions of Master Node 1 and Node 3, Node 2 transmitsits second data packet, according to the TDMA scheduling.

Since after the second frame the transmission coordinator received datapackets from all the nodes/sensor devices included in the associatedtyre, no more beacons comprising timing information are sent in thesubsequent frames. Then, data transmission goes on according to the TDMAscheduling in the subsequent frames, up to the end of the transmissionwindow.

Example 2

FIG. 4 shows a second exemplary sequence of time frames for thecoordinated data transmission of three nodes/sensor devices located onthe same meridian plane of a tyre. It is assumed that a beacon(represented by “B” in FIG. 4) including timing information is sentthree times by a transmission coordinator associated to the threenodes/sensor devices at the beginning of a time window provided for dataacquisition. It is also assumed that data transmission is performedafter the end of data acquisition.

The timing of the start of the transmission window could be dictated bya suitable parameter T_(—tx) included in the beacon. The beaconincluding timing information is sent three times in sequence by thetransmission coordinator in order to reduce (or even nullify) theprobability of non-reception of the beacon by the nodes/sensor devices.In this exemplary communication protocol, in fact, the transmissioncoordinator does not have an acknowledgement of the reception of thebeacon by the nodes/sensor devices (which is advantageous, even if notmandatory, in order to save power consumption).

As shown by FIG. 4, all the Nodes receive the beacon including timinginformation. Consequently, they switch off their receiver and begin toacquire the data to be transmitted in the following transmission timewindow. The Nodes also calculate the assigned timeslots for subsequentdata transmission. Then, when the start of the transmission windowoccurs (represented by T _(—) _(tx) in FIG. 4), each Node (the MasterNode 1 first, then the Node 2, and then Node 3) transmits data packetsin the respective assigned timeslot, in each frame of the transmissionwindow.

Example 3

FIG. 5 shows a third exemplary sequence of time frames for theretransmission of lost data packets transmitted by three nodes/sensordevices located on the same meridian plane of the tyre. It is assumedthat the communication protocol provides for a retransmission window atthe end of the transmission window. For example, such retransmissionwindow could last 10% of the transmission window. The timing informationfor enabling the nodes/sensor devices to correctly set theretransmission window could be sent in the beacon sent by thetransmission coordinator or permanently stored in the memory of thenodes/sensor devices. However, differently from the transmissions of thedata packets, retransmissions do not follow a TDMA schedule, but areperformed by the nodes/sensor devices on request received by thetransmission coordinator.

It is assumed that at the end of the transmission window eachnode/sensor device switches on its respective receiver for listening forpossible retransmission request beacons coming from the associatedtransmission coordinator. Preferably, during listening operation, eachnode/sensor device switches off its respective transmitter.

It is also assumed that the transmission coordinator sends theretransmission request beacons by addressing them to the nodes, usingthe respective identifiers.

With reference to the exemplary sequence of FIG. 5, at the end of thetransmission window the transmission coordinator sends a retransmissionrequest beacon addressed to (i.e. labeled with the identifier of) MasterNode 1 (RB1) requesting retransmission of some lost data packets, andswitches to a listen status for receiving the packet(s) retransmitted byMaster Node 1 (R_TX). Master Node 1 receives the retransmission requestbeacon RB1 addressed to it and retransmits the lost data packetsdictated by the retransmission request beacon. As shown in FIG. 5,during retransmission, another missing reception occurs at thetransmission coordinator (indicated by X in FIG. 5). After theretransmission, Master Node 1 switches off its transmitter and switcheson its receiver for listening to further retransmission request beacons.

After the completion of the retransmission of Master Node 1, thetransmission coordinator sends a retransmission request beacon addressedto (i.e. labeled with the identifier of) Node 2 (RB2). Node 2, which islistening to possible retransmission requests coming from thetransmission coordinator, misses the retransmission request beacon RB2(as indicated by XXX in FIG. 5), and continues listening.

After a predetermined elapsed time, the transmission coordinator sends aretransmission request beacon addressed to (i.e. labeled with theidentifier of) Node 3 (RB3). Node 3, which is listening to possibleretransmission requests coming from the transmission coordinator,receives the retransmission request beacon RB3 addressed to it andretransmits the lost data packets dictated by the retransmission requestbeacon. After the retransmission, Node 3 switches off its transmitterand switches on its receiver for listening to further retransmissionrequest beacons.

After the completion of the retransmission of Node 3, the transmissioncoordinator sends another retransmission request beacon addressed to(i.e. labeled with the identifier of) Master Node 1 (RB1), requestingretransmission of the previously missed retransmitted packet. MasterNode 1 receives the retransmission request beacon RB1 addressed to itand retransmits the lost data packets dictated by the retransmissionrequest beacon.

After the completion of the retransmission of Master Node 1, thetransmission coordinator sends another retransmission request beaconaddressed to (i.e. labeled with the identifier of) Node 2 (RB2). Node 2,which is listening to possible retransmission requests coming from thetransmission coordinator, receives the retransmission request beacon RB2addressed to it and retransmits the lost data packets dictated by theretransmission request beacon.

The retransmission phase continues until either all lost data packetsare successfully received at the transmission coordinator or the end oftransmission window is reached.

The present invention has been described considering some possibleembodiments thereof. Those skilled in the art will readily recognizethat several modifications to the described embodiments are possible, aswell as other embodiments, all falling within the scope of the appendedclaims.

For example, although the description has been carried out withparticular reference to transmission from a single tyre, transmissionfrom different tyres is also encompassed by the present invention.Exemplarily, transmission from sensor devices included in differenttyres could be carried out by exploiting CDMA (Code Division MultipleAccess) for separating the different signals, or also FDMA (FrequencyDivision Multiple Access).

Moreover, transmission from different groups of sensor devices includedin a single tyre as in the embodiment shown in FIG. 2 could be carriedout by designated one sensor device in each group as being the masternode/sensor device of the group. This master node may initiatetransmission of beacons on behalf of its group when it is ready tooperate, so that the transmission coordinator could at leastapproximately gain information on the location in the tyre of eachgroup. The number of groups may determine the maximum allowed timeinterval for each group of sensor devices, and each group of sensordevices may practically have the same transmission TDMA structure (inparticular if the number of sensor devices is equal in all groups). Inpreferred embodiments, TDMA structure is accomplished so as no overlapis provided between the transmission intervals assigned to each group ofsensor devices. Clearly, the TDMA structure should provide timeslots ofenough time for allowing each sensor device included in the tyre totransmit at least one data packet to the transmission coordinator.

The invention claimed is:
 1. A method for managing transmission of datafrom a plurality of sensor devices in a tyre fitted on a vehicle,comprising: providing said plurality of sensor devices at predefinedrespective positions in said tyre; providing a transmission coordinatoron said vehicle, outside of said tyre; rotating said tyre and havingsaid plurality of sensor devices obtaining data related to a conditionof said tyre during rotation thereof; and causing said plurality ofsensor devices to wirelessly transmit the obtained data, wherein causingsaid plurality of sensor devices to wirelessly transmit said obtaineddata comprises: sending timing information from said transmissioncoordinator, said timing information being at least related to a maximumallowed time interval for transmission of obtained data from saidplurality of sensor devices; at each sensor device of said plurality ofsensor devices, receiving said timing information and calculating atleast one respective transmission timeslot for the transmission of theobtained data within said maximum allowed time interval, so as to obtaina respective plurality of non-overlapping transmission timeslots; and ateach sensor device of the plurality of sensor devices, waiting forrespective calculated at least one transmission timeslot and wirelesslytransmitting the obtained data within the respective calculated at leastone transmission timeslot.
 2. The method according to claim 1, whereinsaid maximum allowed time interval is at most equal to a time intervalrequired for one complete revolution of said tyre.
 3. The methodaccording to claim 2, wherein said maximum allowed time interval is atmost equal to a half of said time interval required for one completerevolution of said tyre.
 4. The method according to claim 1, furthercomprising sending idle information from at least one master sensordevice of the plurality of sensor devices, wherein said idle informationis related to a readiness of said plurality of sensor devices to receivesaid timing information, and wherein said sending of timing informationfrom said transmission coordinator is performed consequently of areception of said idle information by said transmission coordinator. 5.The method according to claim 1, wherein each sensor device of saidplurality of sensor devices comprises an electrical circuit capable ofbeing adapted to store electrical energy generated in consequence of therotation of the tyre.
 6. The method according to claim 5, furthercomprising sending idle information from at least one master sensordevice of the plurality of sensor devices, wherein said idle informationis related to a readiness of said plurality of sensor devices to receivesaid timing information, and wherein said sending of timing informationfrom said transmission coordinator is performed consequently of areception of said idle information by said transmission coordinator,wherein said sending of idle information is performed by the at leastone master sensor device when a voltage across its respective electricalcircuit is higher than a predetermined threshold.
 7. The methodaccording to claim 1, wherein said timing information sent by saidtransmission coordinator is further related to a maximum allowedacquisition time interval for acquisition of data related to a conditionof said tyre by the plurality of sensor devices.
 8. The method accordingto claim 7, wherein said maximum allowed acquisition time interval and aplurality of non-overlapping calculated transmission timeslots do notoverlap with each other.
 9. The method according to claim 1, furthercomprising receiving, at said transmission coordinator, the obtaineddata transmitted from said plurality of sensor devices, and processingsaid data so as to derive a condition of said tyre.
 10. The methodaccording to claim 9, wherein, in case of missed reception of at leastone data portion transmitted from at least one sensor device, furthercomprising having the transmission coordinator addressing aretransmission request of said data portion to said at least one sensordevice.
 11. The method according to claim 10, further comprisingretransmitting said data portion by said at least one sensor deviceconsequently of a reception thereof of said retransmission request, saidretransmitting being performed within said maximum allowed timeinterval.
 12. The method according to claim 11, wherein saidretransmitting is performed by said at least one sensor device within arespective retransmission timeslot calculated by said at least onesensor device based on said timing information, and wherein saidcalculated respective retransmission timeslot and said plurality ofnon-overlapping transmission timeslots do not overlap with each other.13. The method according to claim 11, wherein providing said pluralityof sensor devices at predefined respective positions in said tyrecomprises disposing at least two sensor devices substantially at a samemeridian plane of the tyre.
 14. A system for monitoring a tyre fitted ona vehicle comprising: a plurality of sensor devices capable of beingadapted to obtain data related to a condition of said tyre duringrotation thereof and to wirelessly transmit obtained data outside ofsaid tyre; and a transmission coordinator capable of being adapted toreceive said obtained data transmitted by said plurality of sensordevices, wherein said transmission coordinator is further capable ofbeing adapted to send timing information to said plurality of sensordevices, said timing information being at least related to a maximumallowed time interval for the transmission of the obtained data fromsaid plurality of sensor devices; each sensor device of said pluralityof sensor devices is further capable of being adapted to receive saidtiming information and calculate at least one respective transmissiontimeslot for the transmission of the obtained data within said maximumallowed time interval, so as to obtain a respective plurality ofnon-overlapping transmission timeslots; and each sensor device of theplurality of sensor devices is further capable of being adapted to waitfor a respective calculated at least one transmission timeslot and towirelessly transmit the obtained data within the respective calculatedat least one transmission timeslot.
 15. The system according to claim14, wherein said maximum allowed time interval is at most equal to atime interval required for one complete revolution of said tyre.
 16. Thesystem according to claim 15, wherein said maximum allowed time intervalis at most equal to a half of said time interval required for onecomplete revolution of said tyre.
 17. The system according to claim 14,wherein at least one master sensor device is further capable of beingadapted to send idle information, said idle information being related toa readiness of said plurality of sensor devices to receive said timinginformation, and wherein said transmission coordinator is furthercapable of being adapted to send said timing information consequently ofa reception of said idle information.
 18. The system according to claim14, wherein each sensor device of said plurality of sensor devicescomprises an electrical circuit capable of being adapted to storeelectrical energy generated in consequence of the rotation of the tyre.19. The system according to claim 18, wherein at least one master sensordevice is further capable of being adapted to send idle information,said idle information being related to a readiness of said plurality ofsensor devices to receive said timing information, and wherein saidtransmission coordinator is further capable of being adapted to sendsaid timing information consequently of a reception of said idleinformation, and wherein at least one master sensor device is capable ofbeing adapted to send said idle information when a voltage across arespective electrical circuit thereof is higher than a predeterminedthreshold.
 20. The system according to claim 14, wherein said timinginformation is further related to a maximum allowed acquisition timeinterval for the acquisition of data related to a condition of said tyreby the plurality of sensor devices.
 21. The system according to claim20, wherein said maximum allowed acquisition time interval and aplurality of non-overlapping calculated transmission timeslots do notoverlap with each other.
 22. The system according to claim 14, whereinsaid transmission coordinator is further capable of being adapted toprocess said data so as to derive a condition of said tyre.
 23. Thesystem according to claim 22, wherein the transmission coordinator isfurther capable of being adapted to address a retransmission request ofat least one data portion to at least one sensor device in case ofmissed reception of said at least one data portion transmitted from atleast one sensor device.
 24. The system according to claim 23, whereinsaid at least one sensor device is further capable of being adapted toretransmit said at least one data portion in consequence of a receptionof said retransmission request, said retransmitting being performedwithin said maximum allowed time interval.
 25. The system according toclaim 24, wherein said at least one sensor device is further capable ofbeing adapted to calculate a respective retransmission timeslot based onsaid timing information and to retransmit said at least one data portionwithin said respective calculated retransmission timeslot, and whereinsaid calculated respective retransmission timeslot and said plurality ofnon-overlapping transmission timeslots do not overlap with each other.26. The system according to claim 14, wherein said plurality of sensordevices comprises at least two sensor devices disposed substantially ata same meridian plane of the tyre.
 27. The system according to claim 14,wherein each sensor device of said plurality of sensor devices comprisesan accelerometer.
 28. The system according to claim 27, wherein saidaccelerometer is capable of being adapted to measure acceleration in atleast two directions or three directions.
 29. The system according toclaim 14, wherein each sensor device of said plurality of sensor devicesis fixed to an inner surface of the tyre.